phantom to test muga software bill thomson, joe o’brien nigel williams

Phantom to test MUGA software

Bill Thomson , Joe O’BrienNigel Williams

Not New!

Phantom developed some years ago

need to test amplitude and phase component

not designed for ejection fraction

Normal / Abnormal MUGA scan

Single Harmonic Fourier

At each pixel position, we fit a curve based on first term of Fourier series

a + b.sin(t) + c.cos(t)

= A.sin(t + )

the first harmonic is a sinusoid function with the fundamental frequency and a phase angle .

Sum of Cos and Sin terms

+ =

Sum of Cos and Sin terms

+ =

Sum of Cos and Sin terms

• Frequency does not change• phase change only

+ =

Sum of Cos and Sin terms

• Frequency does not change• phase change only

+ =

Single harmonic Fourier fit

0

20

40

60

80

100

120

1 5 9 13 17 21

A

For each pixel,

AAmplitude functional imageextent of change

Phase functional imagetiming

Amplitude and Phase

Amplitude

how much movement

Phase

onset of contraction

15% threshold (from amplitude)

histogram of phase in -

whole image

ED L ventricle region

Test Procedure

Need to input sinusoid terms

want amplitude range 0 - 100%

want phase values 0 - 360

Sinusoid shape

A A

Sinusoid shape

A A

Curves generated

Curves generated

rotating plane phantom

Amplitude and phase

Amplitude and phase

Phase direction

note 90 degree shift in phase angle

Phase should follow the phantom

Phase is actually going in opposite direction

Change of ED ROI

Effect of change in ED position

Different ROI position

Phantom for EF curve creation

• Perimeter of phantom based on EF curve

• similar effects seen

• shows robust Fourier fit at low ejection fraction and counts

Previous work - different processor

Area of LV was delayedphase shows early contraction!!phase was reversed

Previous work - different processor

Area of LV was delayedphase shows early contraction!!phase was reversed

Corrected program

Higher Harmonic testing

1st harmonic

Higher Harmonic testing

1st harmonic 2nd harmonic

Higher Harmonic testing

1st harmonic

3rd harmonic

2nd harmonic

3 Harmonic phantom

3 harmonic phantom

Fourier curve fit tries to fit first EF type component only

3 harmonic phantom , different ROI

3 harmonic phantom , different ROI

3 harmonic fit to noisy data

Issues

• Phase angle appears to run in wrong direction

• Will not affect aneurism detection

• Amplitude and phase dependent on ROI

• Fourier fits to CDBS curve

• Time to Peak Fill is based on Fourier curve

• Suggest use 4 harmonic fit routinely